GPR40 is a seven transmembrane receptor that is expressed in a great number of tissues including the pancreatic islet cells, brain and gastrointestinal tract. The ligand stimulating this receptor is felt to be medium chain fatty acids. During the past year we have succeeded in creating mice with homozygous deletion of the majority of the coding exon for the GPR40 gene and expressing the enhanced form of the green fluorescent protein as a fusion protein following the first 15 amino acids of GPR40.